Reference voltage adjustment for word line groups

Abstract

Methods, systems, and devices for reference voltage adjustment for word line groups are described. In some examples, one or more components of a memory system may determine a duration that data has been stored to one or more memory cells. Based on the duration, a voltage value of one or more reference voltages may be adjusted accordingly. For example, a voltage value of one or more reference voltages may be adjusted based on the duration. Moreover, the reference voltage values may be adjusted differently in response to the memory cells having stored data for a relatively longer duration, as opposed to memory cells that have stored data for a relatively shorter duration. The adjusted reference voltages may be used during a subsequent read operation. The voltage value of the one or more reference voltages may be adjusted on a word-line group by word-line group basis.

What is claimed is: 
     
       1. An apparatus, comprising:
 a controller associated with a memory device, wherein the controller is configured to cause the apparatus to:
 write, at a first time, data to at least one memory cell of a first plurality of memory cells, wherein the first plurality of memory cells is coupled with a first word line that is associated with a block of memory cells; 
 initiate, at a second time after the first time, a read operation to read the data based at least in part on writing the data; 
 determine a duration between the first time and the second time based at least in part on initiating the read operation; 
 adjust a first plurality of reference voltage values of a first plurality of reference voltages associated with the first word line associated with the block that stores the data and a second plurality of reference voltage values of a second plurality of reference voltages associated with a second word line associated with the block that stores the data based at least in part on determining the duration between the first time and the second time, wherein the first plurality of reference voltage values are different than the second plurality of reference voltage values; and 
 read the data from the at least one memory cell associated with the first word line based at least in part on adjusting the first plurality of reference voltage values and the second plurality of reference voltage values. 
 
 
     
     
       2. The apparatus of  claim 1 , wherein the controller is further configured to cause the apparatus to:
 determine a first set of adjustments of a third plurality of reference voltage values based at least in part on the duration between the first time and the second time, the first set of adjustments used by each memory cell in the block of memory cells, wherein the third plurality of reference voltage values comprises the first plurality of reference voltage values and the second plurality of reference voltage values, and wherein adjusting the first plurality of reference voltage values and the second plurality of reference voltage values is based at least in part on the first set of adjustments. 
 
     
     
       3. The apparatus of  claim 2 , wherein the controller is further configured to cause the apparatus to:
 determine a second set of adjustments of the first plurality of reference voltage values based at least in part on determining the first set of adjustments, wherein the second set of adjustments comprises adjusting a respective plurality of reference voltage values for each word line associated with the block of memory cells, and wherein adjusting the first plurality of reference voltage values is based at least in part on the second set of adjustments. 
 
     
     
       4. The apparatus of  claim 3 , wherein determining the second set of adjustments of the first plurality of reference voltage values is configured to cause the apparatus to:
 adjust the first plurality of reference voltage values associated with the first plurality of memory cells; and 
 refrain from adjusting the second plurality of reference voltage values associated with a second plurality of memory cells. 
 
     
     
       5. The apparatus of  claim 2 , wherein the controller is further configured to cause the apparatus to:
 determine that an adjustment of the first plurality of reference voltage values exceeds a threshold voltage value adjustment based at least in part on determining the duration between the first time and the second time; and 
 determine a second set of adjustments of the third plurality of reference voltage values associated with the block of memory cells based at least in part on determining the second set of adjustments of the third plurality of reference voltage values, wherein adjusting the first plurality of reference voltages associated with the first plurality of memory cells is based at least in part on determining the second set of adjustments of the third plurality of reference voltage values. 
 
     
     
       6. The apparatus of  claim 2 , wherein the controller is further configured to cause the apparatus to:
 identify an adjustment index associated with the first word line associated with the block based at least in part on determining the duration between the first time and the second time, wherein the adjustment index indicates a third set of adjustments of the third plurality of reference voltage values, and wherein adjusting the first plurality of reference voltage values is based at least in part on the third set of adjustments. 
 
     
     
       7. The apparatus of  claim 1 , wherein the controller is further configured to cause the apparatus to:
 initiate a timer based at least in part on writing the data to the at least one memory cell of the first plurality of memory cells at the first time, wherein the duration between the first time and the second time is based at least in part on initiating the timer. 
 
     
     
       8. The apparatus of  claim 1 , wherein a first reference voltage of the first plurality of reference voltages distinguishes between a first state and a second state capable of being stored by a memory cell and a second reference voltage of the first plurality of reference voltages distinguishes between the second state and a third state capable of being stored by the memory cell. 
     
     
       9. The apparatus of  claim 8 , wherein:
 the memory cell is configured to store three bits of information using eight states. 
 
     
     
       10. The apparatus of  claim 8 , wherein adjusting the first plurality of reference voltages associated with the first plurality of memory cells is configured to cause the apparatus to:
 adjust a value of the first reference voltage by a first value; and 
 adjust a value of the second reference voltage by a second value that is different than the first value. 
 
     
     
       11. The apparatus of  claim 1 , wherein at least the first plurality of memory cells are not accessed during the duration between the first time and the second time. 
     
     
       12. The apparatus of  claim 1 , wherein a second plurality of memory cells coupled with the second word line are associated with the block of memory cells. 
     
     
       13. The apparatus of  claim 1 , wherein the controller is further configured to cause the apparatus to:
 receive a read command to read the data, wherein initiating the read operation is based at least in part on receiving the read command. 
 
     
     
       14. A non-transitory computer-readable medium storing code comprising instructions which, when executed by a processor of an electronic device, cause the electronic device to:
 write, at a first time, data to at least one memory cell of a first plurality of memory cells, wherein the first plurality of memory cells is coupled with a first word line that is associated with a block of memory cells; 
 initiate, at a second time after the first time, a read operation to read the data based at least in part on writing the data; 
 determine a duration between the first time and the second time based at least in part on initiating the read operation; 
 adjust a first plurality of reference voltage values of a first plurality of reference voltages associated with the first word line associated with the block that stores the data and a second plurality of reference voltage values of a second plurality of reference voltages associated with a second word line associated with the block that stores the data based at least in part on determining the duration between the first time and the second time, wherein the first plurality of reference voltage values are different than the second plurality of reference voltage values; and 
 read the data from the at least one memory cell associated with the first word line based at least in part on adjusting the first plurality of reference voltage values and the second plurality of reference voltage values. 
 
     
     
       15. The non-transitory computer-readable medium of  claim 14 , wherein the instructions, when executed by the processor of the electronic device, further cause the electronic device to:
 determine a first set of adjustments of a third plurality of reference voltage values based at least in part on the duration between the first time and the second time, the first set of adjustments used by each memory cell in the block of memory cells, wherein the third plurality of reference voltage values comprises the first plurality of reference voltage values and the second plurality of reference voltage values, and wherein adjusting the first plurality of reference voltage values and the second plurality of reference voltage values is based at least in part on the first set of adjustments. 
 
     
     
       16. The non-transitory computer-readable medium of  claim 15 , wherein the instructions, when executed by the processor of the electronic device, further cause the electronic device to:
 determine a second set of adjustments of the first plurality of reference voltage values based at least in part on determining the first set of adjustments, wherein the second set of adjustments comprises adjusting a respective plurality of reference voltage values for each word line associated with the block of memory cells, and wherein adjusting the first plurality of reference voltage values is based at least in part on the second set of adjustments. 
 
     
     
       17. The non-transitory computer-readable medium of  claim 16 , wherein the instructions to determine the second set of adjustments of the first plurality of reference voltage values, when executed by the processor of the electronic device, further cause the electronic device to:
 adjust the first plurality of reference voltage values associated with the first plurality of memory cells; and 
 refrain from adjusting the second plurality of reference voltage values associated with a second plurality of memory cells. 
 
     
     
       18. The non-transitory computer-readable medium of  claim 15 , wherein the instructions, when executed by the processor of the electronic device, further cause the electronic device to:
 determine that an adjustment of the first plurality of reference voltage values exceeds a threshold voltage value adjustment based at least in part on determining the duration between the first time and the second time; and 
 determine a second set of adjustments of the third plurality of reference voltage values associated with the block of memory cells based at least in part on determining the second set of adjustments of the third plurality of reference voltage values, wherein adjusting the first plurality of reference voltages associated with the first plurality of memory cells is based at least in part on determining the second set of adjustments of the third plurality of reference voltage values. 
 
     
     
       19. The non-transitory computer-readable medium of  claim 15 , wherein the instructions, when executed by the processor of the electronic device, further cause the electronic device to:
 identify an adjustment index associated with the first word line associated with the block based at least in part on determining the duration between the first time and the second time, wherein the adjustment index indicates a third set of adjustments of the third plurality of reference voltage values, and wherein adjusting the first plurality of reference voltage values is based at least in part on the third set of adjustments. 
 
     
     
       20. The non-transitory computer-readable medium of  claim 14 , wherein the instructions, when executed by the processor of the electronic device, further cause the electronic device to:
 initiate a timer based at least in part on writing the data to the at least one memory cell of the first plurality of memory cells at the first time, wherein the duration between the first time and the second time is based at least in part on initiating the timer. 
 
     
     
       21. The non-transitory computer-readable medium of  claim 14 , wherein a first reference voltage of the first plurality of reference voltages distinguishes between a first state and a second state capable of being stored by a memory cell and a second reference voltage of the first plurality of reference voltages distinguishes between the second state and a third state capable of being stored by the memory cell. 
     
     
       22. The non-transitory computer-readable medium of  claim 21 , wherein:
 the memory cell is configured to store three bits of information using eight states. 
 
     
     
       23. The non-transitory computer-readable medium of  claim 21 , wherein the instructions to adjust the first plurality of reference voltages associated with the first plurality of memory cells, when executed by the processor of the electronic device, further cause the electronic device to:
 adjust a value of the first reference voltage by a first value; and 
 adjust a value of the second reference voltage by a second value that is different than the first value. 
 
     
     
       24. The non-transitory computer-readable medium of  claim 14 , wherein at least the first plurality of memory cells are not accessed during the duration between the first time and the second time. 
     
     
       25. A method, comprising:
 writing, at a first time, data to at least one memory cell of a first plurality of memory cells, wherein the first plurality of memory cells is coupled with a first word line that is associated with a block of memory cells; 
 initiating, at a second time after the first time, a read operation to read the data based at least in part on writing the data; 
 determining a duration between the first time and the second time based at least in part on initiating the read operation; 
 adjusting a first plurality of reference voltage values of a first plurality of reference voltages associated with the first word line associated with the block that stores the data and a second plurality of reference voltage values of a second plurality of reference voltages associated with a second word line associated with the block that stores the data based at least in part on determining the duration between the first time and the second time, wherein the first plurality of reference voltage values are different than the second plurality of reference voltage values; and 
 reading the data from the at least one memory cell associated with the first word line based at least in part on adjusting the first plurality of reference voltage values and the second plurality of reference voltage values.